Switching power converters are widely used in a large number of domestic and industrial applications. Examples include computer systems, motor drives, and uninterruptible power supplies. With recent advances in semiconductor technologies and electronic packaging techniques, much research work has been done on new power circuit topologies, switching schemes, and control techniques for improving the converter efficiency, electrical specifications, and power density--all the time meeting various industrial standards. Examples of well known power converter topologies include buck converters, boost converters, buck boost converters, flyback converters and forward converters.
An underlying concept of power electronics is to be able to use low-level signals to control high power converter outputs. Conventionally this requires a comparison of the actual output voltage with a desired reference voltage and then giving commands to the power converters. However, it is a common practice that the power conversion stage and the control circuit be isolated in order to avoid noise coupling and grounding problems. In some situations input and output isolation in the power conversion stage is also desirable or necessary. These isolation requirements mean that signal-power interface techniques such as transformer coupling and optical isolation are necessary to achieve output regulation. These requirements substantially increase the cost and complexity of power converters.